By Alan Murray, President, Pew Research Center

This op-ed was published in The Wall Street Journal on July 18, 2013.

The mass uprisings this summer in Egypt, Turkey and Brazil are powerful reminders that the middle classes drive history. What remains unclear, however, is where they are driving it.

The world today is witnessing its third great surge of middle-class growth. The first was brought about in the 19th century by the Industrial Revolution; the second surge came in the years following World War II. Both unfolded primarily in the United States and Europe.

The third seems likely to be the biggest and broadest. It has unfolded in China over the past decade but is rapidly spreading through Asia, Latin America and even Africa. Some predict that within two decades, a majority of the world’s population will have middle-class means and desires—for education, cellphones, cars and, most important, the ability to focus on something other than basic food and shelter. It is these millions of people whose hopes and frustrations will shape the future.

Expectations among this group are running high. When the Pew Research Center surveyed nearly 40,000 people in 39 countries this spring, we asked the quintessential question of middle-class aspiration: Will children in your country be better off than their parents? Large majorities in most advanced economies said “no.” Only 33% of Americans think children will be better off than their parents. The number was 17% in Britain, 15% in Japan and 9% in France.

But in China, 82% now expect their children to live better, and in Brazil, 79% think the same way. Majorities in Chile, Malaysia, Venezuela, Indonesia, the Philippines, Nigeria, Ghana and Kenya believe that the next generation will be better off than the current one.

There is little question that this new middle class will change the world. Less clear is how they’ll do it. The all-too-easy assumption in the West has been that these new entrants to the middle-class club will embrace the same values their predecessors did. But evidence on that is mixed.

Many hoped the “Arab Spring” would mean progress toward adopting Western ideas about democracy and human rights. But subsequent events in Egypt—with the recent protests fueled largely by middle-class discontent—revealed how tenuous such hopes may be. Pew surveys in Egypt show that there is public support for democratic rights and institutions, but less support for notions like women’s rights, a civilian-controlled military, and the separation of religion and government. Throughout the Arab world, our research based on available public records shows that the Arab uprisings have led to more restrictions on religion, not fewer.

Another interesting question is to whom or to what these emerging middle-class populations will look for role models. Again, the evidence is mixed. In the emerging countries we surveyed, most people believe that the United States is still the world’s leading economic power. But as a group, they had a somewhat more favorable opinion of China than of the U.S.

In Malaysia, for instance, 81% of those surveyed had a favorable opinion of China, compared with only 55% who had a positive view of the U.S. In Indonesia, 70% had a favorable opinion of China, compared with 61% for the U.S. Even in America’s own hemisphere, 65% of Brazilians had a favorable opinion of China, not far behind the 73% for the U.S. Argentines and Venezuelans gave China more positive marks.

Those favorability measures, of course, paint with a broad brush. The people in emerging markets specifically give the U.S. high grades—and higher than China’s—for respecting the personal freedoms of its citizens. But the gap between perceptions of the U.S. and China on these issues was much smaller in emerging countries than it was in the developed countries. In the emerging countries, a median of 65% said the U.S. respected personal freedoms, while 41% said the same about China. In developed countries, 79% said the U.S. respected personal freedoms, compared with only 14% for China.

When people in emerging countries were asked whether it was a good thing that U.S. and Chinese ideas were spreading throughout their countries, the gap got even smaller. A median of 37% in the six countries where we asked this question—South Africa, Brazil, Mexico, Chile, Argentina and Venezuela—said it was good that U.S. ideas were spreading, while 32% said the same about Chinese ideas. And in the same countries, a median of 51% said they liked U.S. ways of doing business, while 42% said the same about China.

What all this means is that the new global middle classes will transform societies, economies and political institutions in ways hard to predict. Unlike the middle-class surges of the 19th century and the post-World War II era, this one will not necessarily be rooted in Western values.